Many indexable cutting inserts used for turning, milling or other metal cutting operations include one or more operative and/or non-operative surfaces having non-planar shapes, for example, having concave, convex, bent, sunken, undulating, curly, or bowed shapes, or other different non-planar shapes. The surfaces assume the non-planar shapes, for example, in order to satisfy various constraints arising from functional and geometrical requirements involved in the design of the cutting insert.
Some indexable, double-sided cutting inserts, for example, have two opposing surfaces, e.g., two opposing side surfaces having identical, non-planar shapes. When such a cutting insert is retained in an insert pocket of a cutting tool, a first of the two opposing surfaces may be an operative surface having an associated cutting edge or cutting corner involved in a cutting operation. The operative surface may, for example, function as a rake surface, or as a clearance surface. The second, opposite surface may be uninvolved directly in the cutting operation, that is it may be a non-operative surface, and function as an engagement surface of the cutting insert, for example, by engaging a supporting wall of the insert pocket. When the cutting insert is indexed, for example, the two opposing surfaces interchange positions and thus assume one another's functionality.
However, e.g., referring to the above example, in some instances functional requirements of the operative surface differ from functional requirements for the engagement surface. Therefore, the identical shape of the two interchangeable surfaces may be appropriate, for example, for the functionality of the operative surface, yet inappropriate for the functionality of the engagement surface. For instance, the non-planar shape of the two surfaces may provide desired clearance, cutting and/or chip forming properties for the operative surface, but at the same time provide only deteriorated engagement between the engagement surface and the supporting wall.
Additionally, e.g., due to ordinary imperfections in the manufacture of the cutting insert, even the aforementioned deteriorated engagement may be achieved only through extensive grinding of a plurality of surfaces and edges of each individual cutting insert. The extensive grinding may be expensive, and additionally result in undesired peeling of a coating layer that covers the cutting insert. In addition, the geometry of some cutting inserts results, for example, in the grinding of the edges of the cutting inserts together with the respective engagement surfaces, even though grinding of the edges is not required, and even undesirable.